1. Field of the Invention
The present invention relates to multiple wiring technologies, and more specifically, to a multiple wiring metal structure employing low-k dielectric material and a method for fabricating such a structure in a semiconductor device.
2. Discussion of the Related Art
Logic IC devices are progressing to achieve higher operational speed and higher integration with a miniaturization of components such as transistors. Such highly integrated transistors require smaller wiring for interconnecting circuit elements and for paths for power supply and signal transmission. Among other limitations, signal delay in the fine metal wires becomes significant in decreasing the operational speed.
Copper having low electric resistance (e.g., 62% than aluminum metal) is used as a material for wiring metal, and material having lower dielectric constant (low-k) is used for insulating or dielectric material between multiple copper metal layers. With these materials, parasitic capacitance between the upper and lower wiring metals is decreased to enable a higher operational speed and to reduce crosstalk between circuit elements. For minimizing the signal delay, it is not sufficient to employ only conductive material having lower resistance, and thus it has to be combined with the interlayer dielectric material of low-k.
Very low-k (VLK) dielectric material having less than “3.0” of dielectric constant may be a candidate for the next generation interlayer dielectric material. This is because the conventional low-k material such as undoped silicate glass (USG) and fluoro-silicate glass (FSG) reveals limits in applying to existing fabrication capability due to signal cross talk as the width and thickness of the interlayer dielectric decreases.
For overcoming the limits, various low-k dielectrics such as carbonate silicate glass (CSG), alpha-fluorinated amorphous carbon (α-FC), and hydrogen silsesquioxane (HSQ) have been developed. However, they reveal problems of, e.g., inferior stability and outgassing in subsequent thermal processes.